This invention relates to spark erosion systems of the type that produce spheres of intermetallic compounds containing rare earth materials, preferably, erbium or dysprosium. Such structures of this type, as described more completely in the following section entitled "Description of the Invention", generally produce a high yield of intermetallic spheres, preferably, in the size range of 150 .mu.m to 400 .mu.m. In particular with respect to the present invention, charges or chunks of alloys of erbium or dysprosium are placed in a high yield spark erosion cell which is located on a shaker table such that when a pulsed voltage is placed upon the electrodes of the spark erosion cell, intermetallic spheres are produced. This invention relates to certain unique intermetallic spheres and the manufacturing means in association therewith.
Prior to the present invention, as set forth in general terms above and more specifically below, it was known, in the manufacturing of cryogenic refrigerator regenerator materials to make use of an atomizing system with the hope of creating regenerator materials that would provide adequate specific heat and density properties. However, due to the inherent nature of the atomizing process, the material was, typically, too small in diameter and created a packing factor with too much density. The preferred diameter for application in a cryogenic refrigerator regenerator is 6-16 mils and the preferred packing factor or amount of volume taken up by the material itself, is 50%. Finally, the atomizing process was not cost efficient because the process requires at least ten pounds of charge material in order to operate efficiently and the amount of material, typically, used in a cryogenic refrigerator regenerator is less than ten pounds. Consequently, a more advantageous system, then, would be presented if such amounts of particle diameter and packing factor could be increased while reducing the amount of waste.
In order to at least attemt to reduce the amount of waste, techniques such as crushing and grinding of the regenerator material were employed. Simply, the material was placed in a container and crushed and ground by conventional techniques. The material was then sifted to separate the particles of different sizes. While this technique reduced the amount of waste because only the amount that was to be used in the regenerator was crushed, ground and sifted, the technique still produced acicular fine particles that had an undesirable packing factor. The particles were acicular mainly because the material used was very brittle which was conducive to creating these acicular particles. Therefore, further increase of the particle diameter and packing factor would be advantageous.
It is apparent from the above that there exists a need in the art for a system which produces cryogenic refrigerator regenerator materials, and which is not wasteful, but which at the same time produces materials which transfer heat efficiently. It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.